1. Field of the Invention
The present invention relates generally to optical fibers (hereinafter fiber), and particularly to fiber coatings.
2. Technical Background
Fiber has acquired an increasingly important role in the field of telecommunications, frequently replacing existing copper wires. This trend has had a significant impact in all areas of telecommunications, which has seen a vast increase in the usage of fiber. Further increases in the use of fiber is at least foreseen in local loop telephone and cable TV service, as local fiber networks are established to deliver ever greater volumes of information in the form of data, audio, and video signals to residential and commercial users. In addition, use of fiber in home and commercial business environments for internal data, voice, and video communications has begun and is expected to increase.
Fibers typically contain a glass core and at least two coatings, e.g. a primary (or inner) coating and a secondary (or outer) coating. The primary coating is applied directly to the glass fiber and, when cured, forms a soft, elastic, and compliant material which encapsulates the glass fiber. The primary coating serves as a buffer to cushion and protect the glass fiber core when the fiber is bent, cabled, or spooled. The secondary coating is applied over the primary coating and functions as a tough, protective outer layer that prevents damage to the glass fiber during processing and use.
Exposure of the fiber to light has caused the appearance of the fiber to change from white or a translucent color to a yellow color. This phenomenon is known as photo-yellowing of the fiber. Photo-yellowing can cause problems with fiber identification, particularly in dimly lit places such as a manhole. Fiber covered with a lighter colored ink, such as light blues (aqua), yellows, or greens, tend to appear as a brown color as the fiber undergoes photo-yellowing.
A need exists to prevent a coated fiber from yellowing.
One aspect of the present invention relates to a coating composition for an optical fiber. The composition includes at least one UV curable monomer, at least one photoinitiator, and at least one ultra-violet light absorber. The inventive coating composition may be applied to an optical fiber to form at least one of the coatings applied to the fiber.
A second aspect of the invention relates to a coating composition for an optical fiber. The composition includes at least one UV curable monomer, at least one photoinitiator, and at least one hindered amine light stabilizer. A third aspect of the invention relates to a coating composition for an optical fiber which includes at least one UV curable monomer, at least one photoinitiator, and at least one optical brightener.
The present invention has the advantage of preventing the photo-yellowing of the coatings applied to an optical fiber. The present invention also improves the ability of a technician to identify the fiber that has been stored in a dimly lit location.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operation of the invention.